1. Field of the Invention
The present invention relates to an illumination apparatus (illuminator), an exposure apparatus, and a method for fabricating devices using the same. In particular, the present invention is suitable for fabricating devices, for example, semiconductor devices such as ICs and LSIs, liquid crystal devices, image devices such as CCDs, and magnetic heads. A titanium oxide (TiO2) film is provided on a portion of an optical unit included in an exposure apparatus such as a projection exposure apparatus (projection aligner) or on a portion of a supporting unit for supporting the optical unit, in order to prevent dust, hazardous substances in the air, and the like from adhering to and contaminating the surface of each unit, even when far ultraviolet light is used as exposure light for long periods of time.
2. Description of the Related Art
With respect to high integration photolithography in fabricating semiconductor devices, there has been a shift in the exposure light used from visible region light to ultraviolet region light. In recent applications of photolithography, a laser such as an excimer laser is used as a light source instead of a mercury lamp. Also, in recent applications of lithography, there has been a shift in the environment in which projection and exposure are performed, from in the air to in a non-oxygen atmosphere, such as a nitrogen, reduced-pressure, or vacuum atmosphere. Chemically amplified resists using acid catalysts are becoming popular. Also, there have been considerable changes in specifications required for optical materials (i.e., optical units) such as optical elements, for example, lenses and mirrors, included in optical systems used for reduction-type projection aligners such as steppers, fabrication apparatuses, and processes.
Chemical contamination in a clean room in which photolithography is performed may be caused by the breakdown of substances by photoreaction of a resist, the scattering of substances during coating, development, baking, cleaning, and other processes, and the vaporization of substances from adhesives and wall materials. These substances float in the air with a considerable density. Because of the substances described above, surfaces of optical elements such as lenses, mirrors, and prisms are considerably contaminated after they are exposed for a long time by KrF or ArF excimer laser light, or deep ultraviolet light. Substance adhering to the surfaces significantly decrease optical properties such as transmittance and reflectance. Generally, these substances vary in shape and composition, and although adhesion is more likely to occur in certain environments, the reasons for adhesion are not clear. It may be inferred from the above that decomposition, recombination, multiple reactions, deposition, crystallization, and the like, act complexly instead of a simple photochemical reaction.
Contamination of optical units is a serious problem, particularly with steppers, which are used for fabrication of semiconductor devices. Contamination also is a serious problem with optical systems for other usages such as lens systems for still cameras, lens systems for video cameras, lens systems for telescopes, and lenses, mirrors, prisms, and diffraction gratings for microscopes and measuring instruments.
It is an object of the present invention to provide an illuminator, an exposure apparatus, and a method for fabricating devices using the same, in which optical properties do not decrease.
In accordance with an illuminator of the present invention, in one aspect, an illuminator for illuminating a surface to be illuminated with a luminous flux from a light source through an illumination system includes a titanium oxide film provided on the surface of at least one unit which constitutes the illumination system;
In another aspect, an illuminator for illuminating a surface to be illuminated with a luminous flux from a light source through an illumination system includes a titanium oxide film provided on the surface of at least one region of at least one optical unit among a plurality of optical units placed in an optical path from the light source to the surface to be illuminated; and
In still another aspect, an illuminator for illuminating a surface to be illuminated with a luminous flux from a light source through an illumination system includes a titanium oxide film provided on the surface of at least one region of at least one supporting unit among a plurality of supporting units for supporting at least one optical unit among a plurality of optical units placed in an optical path from the light source to the surface to be illuminated.
Preferably, in an illuminator of the present invention according to the above aspects,
the luminous flux is ultraviolet light, and the titanium oxide film prevents contaminants, for example, dust and hazardous substances in the air, from adhering to and contaminating the unit provided with the titanium oxide film or its adjacent unit by a photoconductive function such as photoconduction and a photocatalytic reaction caused by the absorption of the ultraviolet light.
The unit or the optical unit includes at least one of a diaphragm, a shutter, and a lens barrel.
The unit or the optical unit includes at least one of a lens, a mirror, a prism, a filter, a diffuser, a diffraction optical element, and an optical integrator.
The unit or the optical unit includes a diffraction optical lens using a diffraction optical element, or a mirror.
The titanium oxide film is provided on the surface of a portion of a region of the optical unit in which light passes through.
The titanium oxide film has a thickness ranging from 10 nm to 100 nm.
In accordance with an exposure apparatus of the present invention, in one aspect, an exposure apparatus for illuminating a pattern on a mask with a luminous flux from a light source through an illumination system and exposing a substrate with the pattern includes a titanium oxide film provided on the surface of at least one unit among a plurality of units which constitute the exposure apparatus;
In another aspect, an exposure apparatus for illuminating a pattern on a mask with a luminous flux from a light source through an illumination system and exposing a substrate with the pattern includes a titanium oxide film provided on the surface of at least one region of at least one optical unit among a plurality of optical units placed in an optical path from the light source to the substrate; and
In still another aspect, an exposure apparatus for illuminating a pattern on a mask with a luminous flux from a light source through an illumination system and exposing a substrate with the pattern includes a titanium oxide film provided on the surface of at least one region of at least one supporting unit among a plurality of supporting units for supporting at least one optical unit among a plurality of optical units placed in an optical path from the light source to the substrate.
Preferably, in an exposure apparatus of the present invention according to the above aspects,
the luminous flux is ultraviolet light, and the titanium oxide film prevents contaminants, for example, dust and hazardous substances in the air, from adhering to and contaminating the unit provided with the titanium oxide film or its adjacent unit by a photoconductive function such as photoconduction and a photocatalytic reaction caused by the absorption of the ultraviolet light.
The unit includes at least one of a diaphragm, a shutter, and a lens barrel.
The unit or the optical unit includes at least one of a lens, a mirror, a prism, a filter, a diffuser, a diffraction optical element, and an optical integrator.
The unit or the optical unit includes a diffraction optical lens using a diffraction optical element, or a mirror.
The titanium oxide film is provided on the surface of a portion of a region of the optical unit in which light passes through.
Exposure is performed while the pattern on the mask and the substrate are synchronously scanned.
The titanium oxide film has a thickness ranging from 10 nm to 100 nm.
In accordance with a method for fabricating devices of the present invention, a method includes the steps of exposing a wafer with a device pattern formed on a reticle using an exposure apparatus according to any one of the above aspects, and developing the wafer.
In accordance with a projection aligner of the present invention, in one aspect, a projection aligner for illuminating a pattern on a mask with a luminous flux from a light source through an illumination system and projecting the pattern onto a wafer by a projection optical system includes a titanium oxide film provided on the surface of at least one unit which constitutes the projection aligner;
In another aspect, a projection aligner for illuminating a pattern on a mask with a luminous flux from a light source through an illumination system and projecting the pattern onto a wafer by a projection optical system includes a titanium oxide film provided on the surface of at least one region of at least one optical unit among a plurality of optical units placed in an optical path from the light source to the wafer; and
In still another aspect, a projection aligner for illuminating a pattern on a mask with a luminous flux from a light source through an illumination system and projecting the pattern onto a wafer by a projection optical system includes a titanium oxide film provided on the surface of at least one region of at least one supporting unit among a plurality of supporting units for supporting one or a plurality of optical units placed in an optical path from the light source to the wafer.
Preferably, in a projection aligner of the present invention according to the above aspects,
the luminous flux is ultraviolet light, and the titanium oxide film prevents contaminants, for example, dust and hazardous substances in the air, from adhering to and contaminating a surface of the unit provided with the titanium oxide film through a photoconductive function such as photoconduction and a photocatalytic reaction caused by the absorption of the ultraviolet light.
The unit includes at least one of a diaphragm, a shutter, and a lens barrel.
The unit includes at least one of a lens, a mirror, a prism, a filter, a diffuser, a diffraction optical element, and an optical integrator.
The unit includes a diffraction optical lens using a diffraction optical element, or a mirror.
The titanium oxide film is provided in a portion of a region through which light passes on the surface of the optical unit.
Projection and exposure are performed while the pattern on the mask and the wafer are synchronously scanned at a velocity ratio in response to imaging magnification of the projection optical system.
The titanium oxide film has a thickness ranging from 10 nm to 100 nm.
In accordance with a method for fabricating devices of the present invention, a method includes the steps of projecting a device pattern formed on a reticle onto a wafer after the reticle is aligned with the wafer using a projection aligner according to any one of the above aspects, and developing the wafer.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.